1. Field of the Invention
The present invention relates to a power zoom lens in which the zooming can be effected during exposure, and a camera system having such a power zoom lens.
This application is related to the commonly assigned applications U.S.S.N. 07/410,880, No. 07/652,038, No. 07/407,424, No. 07/414,477, No. 07/414,478, No. 07/670,733, No. 07/406,523, and No. 07/414,476, the disclosures of which are expressly incorporated by reference herein.
2. Description of Related Art There are various known lens shutter type cameras having a power zoom lens in which the zooming is effected by a motor. A lens shutter type camera having a zooming with exposure function in which the zooming operation is effected with exposure is also known.
However, in a conventional zooming during an exposure operation, since the zooming operation starts at the commencement of exposure, it is impossible to provide a solid image (i.e., base image) when the exposure is effected during the zooming operation. Namely, the entire image of a photographed object is streaked (i.e, blurred). Furthermore, since the zooming speed is constant regardless of the exposure time (i.e., shutter speed), the zooming with exposure is effective only at limited shutter speeds.
Furthermore, it is difficult to realize a single lens reflex camera having a power zoom function, since the incorporation of the power zoom function makes the camera and control system thereof complicated. Therefore, in a conventional single lens reflex camera, the zooming with an exposure can be effected only by manually operating a zoom ring. Accordingly, it is difficult to maintain a constant zooming speed in a single lens reflex camera.
In addition to the foregoing, although it is possible to actuate the shutter during the manual zooming operation, a base image cannot be realized in a photograph. If a photographer attempts to begin the manual zooming after the shutter is actuated, it is very difficult for him or her to determine the timing of the commencement of the zooming at a medium to high shutter speed. Consequently, it is practically impossible to effect a manual zooming with exposure after the shutter is released.